4x4 parity problem

[harshmaul]

Hi cube gurus,

I'm a self taught 3x3 and 4x4 cuber, and the 3x3 is no longer a challenge to me, however i am having dificulties with the 4x4.

I have the whole cube solved except the two center pieces are fliped on one edge.

I am struggling on working out how to solve this, if anybody can shed some light i would be very grateful.

 

[AvGalen]

http://bigcubes.com/4x4x4/finalsolve.html

 

[harshmaul]

Thanks for the link.
now bring on the 5x5!!!